* Igneous rocks are typically crystalline. This means that they are made up of interlocking crystals that have grown from a molten state. The crystals in igneous rocks are often large enough to be seen with the naked eye.
* Igneous rocks are often found in association with other rocks that can be used for radiometric dating. For example, igneous rocks may be found in contact with sedimentary rocks or metamorphic rocks. The ages of these other rocks can help to constrain the age of the igneous rock.
* Igneous rocks are often found in areas that have been geologically active. This means that they have been subjected to high temperatures and pressures, which can alter the composition of the rocks and make them more susceptible to radiometric dating.
When igneous rocks form, they trap radioactive isotopes within their mineral structure. As the radioactive isotopes decay, they produce daughter isotopes that are stable and do not decay further. By measuring the ratio of radioactive isotopes to daughter isotopes in an igneous rock, scientists can calculate the age of the rock.
Radiometric dating is a powerful tool that has been used to date a wide variety of rocks and materials. Igneous rocks are particularly well-suited for radiometric dating, and they have been used to date some of the oldest rocks on Earth.